Dropped __cplusplus guards

littlefs is not a C++ project, and it's important to make sure users are
aware of that in case the header file ever breaks C++ (C++ is _not_
compatible with C99).

So dropping these guards.

C++ users should wrap the relevant includes with extern "C":

  extern "C" {
  #include "lfs.h"
  }

bd/lfs_emubd.h

@@ -14,11 +14,6 @@
 #include "bd/lfs_rambd.h"
 #include "bd/lfs_filebd.h"
 
-#ifdef __cplusplus
-extern "C"
-{
-#endif
-
 
 // Block device specific tracing
 #ifndef LFS_EMUBD_TRACE
@@ -264,8 +259,4 @@ int lfs_emubd_setpowercycles(const struct lfs_config *cfg,
 int lfs_emubd_cpy(const struct lfs_config *cfg, lfs_emubd_t *copy);
 
 
-#ifdef __cplusplus
-} /* extern "C" */
-#endif
-
 #endif